Berlin 2024 – scientific programme

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MA: Fachverband Magnetismus

MA 27: Frustrated Magnets I

MA 27.9: Talk

Wednesday, March 20, 2024, 17:15–17:30, H 2013

Towards a diagrammatic approach to quantum spins — •Björn Sbierski — Universität Tübingen, Germany

Frustrated quantum spin systems in high dimension are one of the central challenges for numerical approaches to quantum many body physics. In this situation a diagrammatic approach based on a pseudo-fermion or pseudo-Majorana spin representation and resummation by the functional renormalization group have provided useful results. However, as two fermions are required to form a single spin operator, this approach lacks efficiency and cannot access spin correlators beyond the two-point object. We present progress towards an alternative diagrammatic approach that directly works with correlation functions of spin operators without any intervening representation of the latter and can also deal with arbitrary spin length S. We discuss the basic diagrammatic rules, definition of vertex ireducibility and various resummation schemes. We present benchmarks of this method and also study spin Hamiltonians of current relevance.

Keywords: diagrammatic methods; functional renormalization group; quantum spins; resummation